Cant I call in a SUITELET from SCA with LOGIN Mode ?

Why not use a service.ss file instead of Suitelet ?

You sure can call a suitelet from a Model/Service. If you need Admin permission or you can elevate the permission of the service you are using to get access to the data you are expecting.

There are additional restrictions when using suitelets using

https.requestSuitelet

that make it no longer available to be called from SCA that way. You can replace the suitelet with a restlet and call using

https.requestResltet

, and if you need to escalate permissions you can do that through increasing permissions directly on the

<http://service.ss|service.ss>

file.